The disclosure of Japanese Patent Application No. 2001-333570 filed on Oct. 30, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a stop valve for closing a fluid passage, more particularly, to a sealing structure of a stop valve with improved sealing performance in closing an opening portion by means of a float.
2. Description of the Related Art
Various kinds of stop valves have been used in various fields for closing fluid passages. In an automobile fuel tank for example, the opening portion which opens inside and outside of the fuel tank has a member provided with a valve body for detecting fuel reaching the opening portion. Consequently, if a vehicle tilts or falls down and thereby the fuel in the fuel tank reaches the opening portion, the member is activated so that the opening portion is closed by the stop valve.
Various kinds of such stop valves have been used. An example of known technology of such a valve is disclosed in Japanese Utility Model Application Laid-Open No.SHO50-134119. The valve is provided with, as shown in FIG. 2A, a valve seat portion 33 having an opening 32 disposed in a fluid passage 31 and a diaphragm 34 disposed facing the opening 32. A valve supporting rod 35 is attached to the diaphragm 34 and a ring-shaped planar valve body 36 is attached to the valve supporting rod 35. Consequently, the diaphragm is pressed by a fluid flowing into the fluid passage 31a, that is a primary pressure, and moves the valve body 36 and the valve supporting rod 35. Then, the valve seat portion 33 is pressed by a surface 37 of the valve body 36 so as to close the opening 32 thereby preventing the fuel from flowing out.
The valve body 36 is made of elastic material. While the valve is not activated, there is provided a gap d, as shown in FIG. 2B, between a back face 38 of the valve body 36 and a top end face 40 of a step portion 39 of the valve supporting rod 35. When the valve is activated as described above and as shown in FIG. 2C, the valve seat portion 33 is pressed by the surface 37 of the bendable valve body 36 so that the opening 32 is securely closed.
A stop valve 41 shown in FIG. 3A is another example of known stop valves. The stop valve 41 has a valve body fixed on a float, in which a passage closing member 42 is provided in a fluid passage leading from the fluid tank to the outside thereof, and a valve seat body 45 having an opening 44 fixed on a frame 43 of the passage closing member 42. A float 47 is disposed in a float guide 46 of the frame 43 such that the float 47 is movable vertically and that the float 47 is supported by the center hole portion of a ring-shaped planar valve body 49 fitted with a valve body supporting portion 48 on the top end portion of the float 47.
In the stop valve 41 provided with the aforementioned float 47, if a fluid is likely to flow out upward through the opening 44 of the valve seat body 45, the float 47 is pulled by the fluid toward the opening side, and thereby a surface 50 of the ring-shaped planar valve body 49 contacts with a ring-shaped sealing protrusion 51 formed on a bottom end portion in the circumference of the opening of the valve seat body 45, thereby closing the opening 44.
As shown in FIG. 3B, the valve body 49 is comprised of a rigid axial portion 52 which is fitted with the valve supporting portion 48 of the float 47, and a ring-shaped planar bendable valve portion 53 which extends outward from the rigid axial portion 52. The rigid axial portion 52 is formed thicker than the bendable valve portion 53, therefore, even when the rigid axial portion 52 is located at the bottom end portion of the valve supporting portion 48 of the float 47 as shown in FIG. 3B, a gap d is provided in a usual condition between the back face of the bendable valve portion 53 and the top end face 54 of the float 47.
In the valve body 49 of such a stop valve of float-actuating type having the aforementioned structure, when the valve is closed as mentioned above, the sealing protrusion 51 of the valve seat body 45 relatively pushes down the surface 50 of the valve body 49 by floating force of the float, thus the bendable valve portion 53 can be bent at least within the gap d and thereby the valve sealing is secured the same as in the valve body shown in FIG. 2.
FIG. 4A shows a stop valve of float-actuating type described above, provided with an improved valve body 55. The valve body 55 has a float sealing portion 57 having three sealing lips as described in the figure, provided particularly on an inner circumference face of the rigid axial portion 56. FIG. 4B shows a partially enlarged view of the valve body 55 installed on a float 58. A center lip 59 located as the center of three sealing lips is formed thicker than other two lips while an upper lip 60 located above the center lip 59 in FIG. 4B is formed thinner than the center lip 59. The upper lip 60 has the shape of a lower half part of the center lip in the example shown in FIG. 4B, therefore the upper lip 60 is a half of the center lip 59 in the thickness. Likewise, a lower lip 61 located under the center lip 59 in the figure has the shape of an upper half part of the center lip 59 thus is a half of the center lip 59 in thickness.
In a stop valve as shown in the aforementioned FIG. 3, a fluid tends to flow out through a gap between the valve body and the float. However, such flowing out can be prevented by forming a valve body into a three-lip shape which can seal the gap by each of the lips. This sealing structure can secure long-term sealing stability at the sealing portion.
To install the valve body of the stop valve, having the aforementioned sealing lips, onto the valve supporting portion 62 of the float 58, a stopper portion 64 of the valve supporting portion 62 is fitted into a center opening 63 of the valve body. The stopper portion 64 is formed on the top end portion of the valve supporting portion 62 and is larger than the valve supporting portion 62 in diameter. In installation such as in automated machine assembly using jigs for example, the sealing lip may be installed in such a posture as the edge is bent due to the friction or other reasons. This may be caused because the edge of the upper lip 60 touches over the back face of the stopper portion 64 until the valve body is completely installed and the center opening 63 is attached onto a predetermined position shown in FIG. 4B, through the stopper portion 64 having a larger diameter as mentioned above.
In another example shown in FIG. 4D, the lower lip 61 may also be installed in such a posture as the edge of the sealing lip bent, not extended completely straight, due to the friction or other reasons that may be caused when the valve body is installed onto a predetermined position shown in FIG. 4B, because the edge of the lower lip 61 presses the surface of the valve supporting portion 62 by elastic force of the valve body, during the lower lip 61 is sliding on the surface of the valve supporting portion.
If the valve body is installed in such a posture as the edge of the sealing lip bent, a predetermined sealing performance each of the sealing lips should exert may not be achieved, and a defect product with bad sealing performance may happen. It would be required therefore to inspect installation failure after installation is finished, however it bothers a lot of time and labor.
Additionally, manual installation may be considered to eliminate such a failure caused in mechanical installation, however, in installing the valve body into such a proper posture as shown in FIG. 4B, a great deal of attention as well as sufficient experience is required, thereby causing product price increase.
The aforementioned problem may be caused also in other cases, not only in the examples mentioned above. The same problem may occur in installation of such a stop valve as the center opening of an intermediate body is to be fitted with the valve supporting member and at the same time a sealing lip is formed on the center opening side.
Accordingly, it is an object of the invention to provide a sealing structure of a stop valve, which prevents the sealing lips from being installed in such a posture as any one of them is bent when the center opening of the valve body having sealing lips is fitted with the valve supporting member of the stop valve.
According to a first aspect of the invention, a stop valve is comprised of: a ring-shaped rigid axial portion; a flat platy bendable valve portion formed thinner than the rigid axial portion and extending outward from the rigid axial portion; and a sealing lip portion extending inward to the rigid axial portion. The sealing lip portion has a first sealing lip and a second sealing lip. The first sealing lip has an extending portion having an axis which extends inward from the rigid axial portion and upward from the bendable valve portion such that it intersects the extending direction of the bendable valve portion. At the edge of the extending portion of the first sealing lip portion, a first seal effecting face of substantially semi-circular shape being contact with an outer circumference face of the supporting portion is formed. The thickness of the extending portion is substantially the same as the diameter of the semi-circular shape of the first seal effecting face. The second sealing lip has an extending portion having an axis which extends inward from the rigid axial portion and downward from the bendable valve portion such that it intersects the extending direction of the bendable valve portion. At the edge of the extending portion of the second sealing lip portion, a second seal effecting face of substantially semi-circular shape being contact with an outer circumference face of the supporting portion is formed. The thickness of the extending portion is substantially the same as the diameter of the semi-circular shape of the second seal effecting face.
According to a second aspect of the invention, a stop valve which is fitted with a cylindrical supporting portion, comprises a ring-shaped rigid axial portion, a platy bendable valve portion formed thinner than the rigid axial portion and extending outward from the rigid axial portion, and a sealing lip portion extending inward from the rigid axial portion. The sealing lip portion comprises a first sealing lip which extends inward from the rigid axial portion up to substantially a same horizontal plane as the top end face of the rigid axial portion and the outer circumference face of the supporting portion, and a second sealing lip which extends inward from the rigid axial portion up to substantially a same horizontal plane as the bottom end face of the rigid axial portion and the outer circumference face of the supporting portion. The each sealing lip comprises a substantially semi-circular seal effecting face provided at an edge thereof and an extending portion having substantially a same thickness as a diameter of the semi-circular shape, connecting the seal effecting face and the rigid axial portion.